An Experimental Investigation into DEF Dosing Strategies for Heavy Duty Vehicle Applications

Copyright © 2015 SAE International.In recent years urea selective catalytic reduction (SCR) has become the principal method of NOx abatement within heavy duty (HD) diesel exhaust systems; however, with upcoming applications demanding NOx reduction efficiencies of above 96 % on engines producing upwards of 10 g·kWh−1 NOx, future diesel exhaust fluid (DEF) dosing systems will be required to operate stably at significantly increased dosing rates. Developing a dosing system capable of meeting the increased performance requirements demands an improved understanding of how DEF sprays interact with changing exhaust flows. This study has investigated four production systems representing a diverse range of dosing strategies in order to determine how performance is influenced by spray structure and identify promising strategies for further development. The construction of an optically accessible hot-air flow rig has enabled visualisation of DEF injection into flows representative of HD diesel exhaust conditions. High-speed and laser sheet imaging have been applied to capture the injection event and analyse spray development within the flows. Results from ambient shadowgraphy show the extent of variation in spray structure that exists between the systems; further quantified with droplet size distribution data collected using phase Doppler interferometry (PDI). Imaging within the exhaust section indicates that the structure of a spray has a significant impact on droplet entrainment within the flow, in turn affecting the level of spray-wall impingement seen. This suggests knowledge of dosing strategy will be critical for optimal system design and enabling near future dosing rate demands to be met.

[1]  Korneel De Rudder,et al.  Tier 4 High Efficiency SCR for Agricultural Applications , 2012 .

[2]  Masahide Takagi,et al.  Study of Spray Distribution and Evaporation and Thermolysis Process of Reductant in Urea SCR , 2011 .

[3]  Z. Gerald Liu,et al.  Thermal and Fluid Dynamic Considerations in Aftertreatment System Design for SCR Solid Deposit Mitigation , 2012 .

[4]  J. Maass,et al.  Influences of AdBlue® spray targeting and mixing devices on the UWS distribution upstream of the SCR catalyst , 2012 .

[5]  T. Johnson,et al.  Review of Selective Catalytic Reduction (SCR) and Related Technologies for Mobile Applications , 2014 .

[6]  Guanyu Zheng,et al.  Evaluation of Mixer Designs for Large Diesel Exhaust Aftertreatment Systems , 2010 .

[7]  Corning,et al.  Vehicular Emissions in Review , 2012 .

[8]  M. Elsener,et al.  Urea-SCR: a promising technique to reduce NOx emissions from automotive diesel engines , 2000 .

[9]  Thomas Lauer,et al.  Optical and Numerical Investigations on the Mechanisms of Deposit Formation in SCR Systems , 2014 .

[10]  Martin Elsener,et al.  NOx-Reduction in Diesel Exhaust Gas with Urea and Selective Catalytic Reduction , 1996 .

[11]  Georg Huthwohl,et al.  A new Approach in AdBlue Dosing to Improve Performance and Durability of SCR Systems for the Use in Passenger Cars up to Heavy Duty Vehicles , 2011 .

[12]  Julien Chapel,et al.  Compact SCR for Passenger Cars , 2011 .

[13]  Alexander Wokaun,et al.  Hydrolysis and thermolysis of urea and its decomposition byproducts biuret, cyanuric acid and melamine over anatase TiO2 , 2012 .

[14]  Guanyu Zheng,et al.  Mixer Development for Urea SCR Applications , 2009 .

[15]  Howard L. Fang,et al.  Urea thermolysis and NOx reduction with and without SCR catalysts , 2003 .

[16]  Stephen F. Benjamin,et al.  Conversion of nitric oxide in an engine exhaust by selective catalytic reduction with a urea spray under steady-state and transient engine-load conditions , 2014 .

[17]  Guanyu Zheng,et al.  Investigation of Urea Deposits in Urea SCR Systems for Medium and Heavy Duty Trucks , 2010 .

[18]  J. Colson,et al.  Thermal decomposition (pyrolysis) of urea in an open reaction vessel , 2004 .

[19]  Donald W. Stanton,et al.  Diesel Engine Technologies Enabling Powertrain Optimization to Meet U.S. Greenhouse Gas Emissions , 2013 .